It just depends on how you look at it. There are the Disney characters that were born princesses, the ones who married princes/kings, and ones who didn't do either but are still cool. The official Disney Princess line includes all of the girls in the picture I posted. Jane, Esmerelda, Alice, Nala, and Wendy aren't a part of that line. And then there's Kida and Eilonwy, who are princesses, but still aren't a part of the Disney Princess line.

I don't really know what Disney's criteria is for picking favorites.